GPIO pins have no predefined purpose, and go unused by default. [1] [2] The idea is that sometimes a system integrator who is building a full system might need a handful of additional digital control lines—and having these available from a chip avoids having to arrange additional circuitry to provide them. For example, the Realtek ALC260 chips ( audio codec ) have 8 GPIO pins, which go unused by default. Some system integrators ( Acer Inc. laptops) use the first GPIO (GPIO0) on the ALC260 to turn on the amplifier for the laptop's internal speakers and external headphone jack .